Move simple Object in Unity 2D

Question

I'm trying to move a simple Object in Unity but I get the following error message:

cannot modify the return value of unityengine.transform.position because itar is not variable

Here is my code:

using UnityEngine;
using System.Collections;

public class walk : MonoBehaviour {
    // Use this for initialization
    void Start () {

    }

    // Update is called once per frame
    void Update () {

        float movespeed = 0.0f;
        movespeed++;
        transform.position.x  = transform.position.x + movespeed;

    }
}

It appears the X property of position is not mutable, can you assign a new Position value instead? eg `transform.position = new Position(transform.position.x + movespeed, transfrom.position.y);` — James, Mar 17 '14 at 23:48
Error CS0246: The type or namespace name 'Position' could not be found (are you missing a using directive or an assembly reference?) (CS0246) (Assembly-CSharp) — Nawaf, Mar 17 '14 at 23:58
All such questions should use `unity3d` tag. The tag `unity` is for a completely different thing. Please learn the tags before using them. — Lex Li, Mar 18 '14 at 02:32

score 26 · Accepted Answer · edited May 23 '17 at 12:10

26

You can't assign the x value on position directly as it's a value type returned from a property getter. (See: Cannot modify the return value error c#)

Instead, you need to assign a new Vector3 value:

transform.position = new Vector3(transform.position.x + movespeed, transform.position.y);

Or if you're keeping most of the coordinate values the same, you can use the Translate method instead to move relatively:

transform.Translate(movespeed, 0, 0)

edited May 23 '17 at 12:10

Community

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answered Mar 18 '14 at 00:28

Chris Sinclair

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it is work ok , but there are another problem , because the object is Directly Disappear after i press Play Game . – Nawaf Mar 18 '14 at 20:05
@Nawaf your computer is too fast! Multiply your movespeed by `Time.deltaTime` to keep it uniform on all CPU speeds. – Dr-Bracket Oct 26 '20 at 19:20

score 2 · Answer 2 · answered Oct 26 '20 at 19:19

A slight improvement over Chris' answer:

transform.position = new Vector2(transform.position.x + movespeed * Time.deltaTime, transform.position.y);

Time.deltaTime the amount of time it's been between your two frames - This multiplication means no matter how fast or slow the player's computer is, the speed will be the same.

Move simple Object in Unity 2D

2 Answers2

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